I have found that my two cats each have a preferred position for being trimmed. One (who has a strong resemblence to a Chartruese) prefers to be on her back, lying in my lap facing me. The other (a proper little jellicle cat) prefers the same position, but facing away (this gives her an advantage in the "bat-at-the-shiny-toy" game).
Both prefer to have their tummies rubbed until they become sleepy, prior to the trimming.
I have also trimmed feral cats for the local Humane Society. If they are tame, the above works nicely. If not, I wrap them in a soft towel and find a paw at a time.